Coral reefs have been described as the tropical rainforests of the sea. They harbour a huge range of bio diversity as well as providing protection to shorelines from coastal erosion. Corals are formed from a symbiotic relationship between Scleractinian Coral and microalgae. Corals come in many different forms, but all are dependent on the relationship with the algae. Coral tends to form in areas of relatively stable sea temperatures around the tropics. In recent years increasing areas of reef have been bleached. This bleaching is caused when the temperature of the sea gets too warm, causing the coral to eject the algae. Once the pigmented algae are rejected the translucent coral then appears white. Reefs can recover from bleaching episodes if they are not too frequent or too severe. As global warming is causing sea temperatures to rise around the planet, more and more areas of reef are suffering bleaching.